The present invention relates to a method for the preparation of at least one layer of a superconducting material with a high transition temperature on the basis of a material system containing metallic components and oxygen. In this method, a layer of a metal-oxide preliminary product of the component of the system with a structure still exhibiting faults with respect to the superconducting metal-oxide phase to be formed is first applied to a predetermined substrate, and the desired superconducting metal-oxide phase is subsequently formed, using a heat treatment in an oxygen atmosphere. Such a method is suggested, for instance, from "Physical Revue Letters", Vol. 58, No. 25, June 22, 1987, pages 2684 to 2686.
Films or thin layers of superconducting metal oxide compounds with high transition temperatures T.sub.c of above 90.degree. K. are generally known. These metal-oxide compounds generally contain several metallic components and oxygen and can have, for instance, a composition of the type Me1-Me2-Cu-O (Me1=rare earths including yttrium; Me2=earth alkali metals). Films with such a composition are frequently prepared by special vapor deposition or sputtering processes. An intermediate product of the components of the chosen material system is deposited on a suitable substrate with a structure which still has faults with respect to the superconducting metal oxide phase to be developed. This preliminary product is subsequently converted into the material with the desired superconducting phase by a heat treatment which must generally be carried out while oxygen is being supplied.
The superconducting metal oxide phases which can be obtained in this manner and the structures of which are similar to those of a perovskite, have an orthorhombic structure in the case of YBa.sub.2 Cu.sub.3 O.sub.7-x with 0&lt;x&lt;0.5 (see, for instance, "Europhysics Letters", Vol. 3, No. 12, June 15, 1987, pages 1301 to 1307). Since these materials having superconducting phases are similar to oxide ceramics, the corresponding high-T.sub.c superconductors are frequently also called oxide-ceramic superconductors.
In addition, it is also known from the publication "Phys. Rev. Lett." mentioned above to prepare monocrystalline films of the system YBa.sub.2 Cu.sub.3 O.sub.7-x on a moncrystalline SrTiO.sub.3 substrate. For this purpose, the three metallic components of the system are vapor-deposited first from separate evaporation sources in an oxygen atmosphere onto the substrate which is at about 400.degree. C. The intermediate product so obtained still has faults with respect to the desired superconducting high-T.sub.c phase. By means of a subsequent heat treatment at a high temperature of about 800.degree. to 900.degree. C. and while oxygen is being supplied, epitaxially grown monocrystalline or at least highly textured film layers with the desired superconducting high-T.sub.c phase are obtained. Films prepared in this manner exhibit a high critical current density of more than 10.sup.5 A/cm.sup.2 at 77.degree. K.
This epitaxy, however, is a necessary condition for the achievement of such high critical current densities which thereby can also open up wide areas of application for such superconducting films. Thus, for instance, such metallizing layers on semiconducting components are conceivable. The mentioned high-temperature process for forming the desired superconducting high-T.sub.c phase, however, is generally not compatible with the usual process steps for the preparation of semiconductor circuits.